Blood vessels become plugged with thrombus or plaque that may ultimately lead to ischemia, a substantial reduction or loss of blood flow to body tissue. A variety of vascular medical devices and procedures have been developed to treat diseased or clogged vessels, including surgical procedures (e.g., bypass surgery where a new blood vessel is grafted around a narrowed or blocked artery), and nonsurgical interventional vascular medical procedures, including angioplasty (where a balloon is inflated inside a narrowed or blocked portion of an artery in an attempt to compress plaque or thrombotic material), stenting (where a metal mesh tube is expanded against a narrowed or blocked portion of an artery to compress plaque or thrombotic material against a vessel wall), and debulking techniques in the form of atherectomy (where a mechanical mechanism dislodges hardened plaque) or thrombectomy (where a mechanical or hydrodynamic mechanism dislodges thrombotic material). In at least some of these interventional vascular medical procedures, a flexible guidewire is routed through the vascular system to a treatment location, and a catheter that includes a distally mounted device appropriate for the given procedure is tracked along the guidewire to the treatment location.
Although interventional vascular procedures avoid many of the complications involved in surgery, there is a possibility of complications if some of the plaque, thrombus or other material breaks free and flows downstream in the artery or other vessel, potentially causing a stroke, a myocardial infarction (heart attack), or other tissue death. One solution to this potential complication is to use an occlusive device or filtering device to block or screen blood from flowing downstream of the treatment location.
In some examples, a protective device such as a balloon can be used. Use of a protective device in conjunction with an atherectomy or thrombectomy device is intended to prevent particulate matter from migrating beyond the protective device and to allow removal of the particulate matter. The balloon is inserted and inflated at a point downstream to the treatment site or lesion site. Therapy is then performed at the site and the balloon acts to block blood flow, which prevents particulate matter from traveling beyond the balloon. Following treatment, some form of particulate removal device is used to remove the dislodged particulates prior to balloon deflation.
Other devices screen blood through a filter arrangement, or strainer. In an example, a strainer device is inserted into a vessel and actuated via a control cable to open and close tines capable of retaining dislodged particulate matter. After treatment, the strainer device is collapsed and the retained particulate matter is removed from the body. In some examples, a nitinol mesh filter is used, or a collapsible filter exhibiting shape memory is used. Such filters are removed by reshaping the collapsible filter, such as by contracting peripheral edges of the filter toward a guidewire, thus reducing a cross section of the filter. In some examples, removal can be via a delivery sheath or other catheter.